The invention relates generally to water-cooled rollers for tunnel or reheat furnaces and more specifically to water-cooled rollers for tunnel or reheat furnaces having integrally cast rollers and intermediate regions disposed on the exterior of a hollow shaft or arbor.
The production of steel billets, bars, plates, slabs and strips may be accomplished continuously through a continuous vertical pour from a tundish which is quickly cooled by water spray and shaped in a series of opposed pairs of rollers. The rollers describe an arc extending from a vertical to a horizontal orientation where the material is sheared into appropriate lengths. Typically, such rapid cooling cools the exterior of the material sufficiently so that it can be handled and treated but leaves the interior at a much higher temperature, in a nearly molten state.
In order to equalize the temperature throughout the metal, it is next provided to a tunnel or reheat furnace which provides both a defined residence time and exterior reheating to achieve temperature uniformity throughout the workpiece in order to facilitate subsequent forming operations. In the tunnel furnace, the metal is moved along a plurality of rollers while being reheated by a plurality of natural gas-fired heaters disposed along the furnace.
Clearly, the service conditions of the rollers, operating in an environment of 2000xc2x0 F. (1095xc2x0 C.) to 2300xc2x0 F. (1260xc2x0 C.), carrying metal bars or slabs at the same temperatures and subjected to cyclic loading from the individual bars or slabs carried thereover are best described as inhospitable. Furthermore, the gas heaters generally operate with excess air and thus the atmosphere within the furnace is an oxidizing atmosphere. Such operating conditions conspire to shorten the operating life of tunnel furnace rollers. Furthermore, while teardown and replacement of such rollers in a furnace is, in itself, costly, the down time of the steel producing facility can represent an even greater expense.
Accordingly, significant effort has been directed to improving the performance and extending the service life of such furnace rollers. U.S. Pat. Nos. 3,860,387 and 4,991,276 teach furnace rollers having inner arbors, outer tubes and tires which support the metal slabs or plates as they pass through the furnace.
U.S. Pat. No. 5,230,618 teaches an insulated furnace roller wherein a refractory is cast about the arbor in regions intermediate the tires which support the slabs or plates in the furnace. Products incorporating the just recited technology exhibit improved service life over prior devices.
From the foregoing, it is apparent that the cost of replacement calculated as both the actual cost of roller replacement and down time of the furnace continues to support efforts to develop and improve tunnel furnace rollers. The present invention is directed to such an improved device.
A tunnel or reheat furnace roller assembly includes a hollow tube or arbor of low alloy steel and an inner concentric tube for providing a flow of cooling water. About the exterior of the tube or arbor is cast a jacket or surround having a plurality of larger diameter, spaced apart wheels which engage and support workpieces in the furnace and integrally formed intermediate smaller diameter regions. The integral surround is preferably cast of Waspaloy or other high temperature, nickel alloy steel. Waspaloy is a trademark of United Technologies, Inc. for its brand of high temperature, nickel alloy steel. The wheels are preferably slightly offset from the longitudinal center of the roller assembly and alternate roller assemblies are reversed end to end when installed in the furnace such that the wheels present an evenly and equally offset or staggered wheel pattern.
Thus it is an object of the present invention to provide a furnace roller having wheels or tires and integrally cast intermediate regions of smaller diameter.
It is a further object of the present invention to provide a furnace roller having integrally cast wheels or tires and intermediate regions of smaller diameter disposed upon a water-cooled tubular shaft or arbor.
It is a still further object of the present invention to provide a furnace roller having integrally cast wheels or tires spaced apart by smaller diameter intermediate regions fabricated of Waspaloy.
It is a further object of the present invention to provide a furnace roller installation wherein wheels of adjacent roller assemblies are arranged in an offset or staggered pattern.
It is a still further objection of the present invention to provide a furnace roller having integrally cast wheels and intermediate regions which exhibit improved service life.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element or feature.